> Am 14.12.2025 um 17:30 schrieb Jeff Law <[email protected]>:
>
>
>
>> On 12/14/25 2:04 AM, Andrew Pinski wrote:
>> So it turns out creating a forwarder block in some cases causes a regression.
>> The rtl ifcvt does like the case were the middle bb does not have a single
>> predecessor.
>> So in some cases ifcvt does not happen any more. So the way to fix this
>> is not to create a forwarder block for those edges which causes out of ssa to
>> create a middle bb which has the constant or the copy in it.
>> I tried to do a simple ifcvt on the gimple level with the last phiopt but
>> that introduces regressions as then `v += cmp - 43;` is not optimized
>> and produces an extra subtraction. This is the best workaround I could come
>> up
>> with until that is fixed. I filed PR 123116 for that issue.
>> Bootstrapped and tested on x86_64-linux-gnu.
>> gcc/ChangeLog:
>> * tree-cfg.cc (ifconvertable_edge): New function.
>> (make_forwarders_with_degenerate_phis): Add skip_ifcvtable argument,
>> check ifconvertable_edge if skip_ifcvtable is true.
>> * tree-cfg.h (make_forwarders_with_degenerate_phis): New argument
>> with default of false.
>> * tree-cfgcleanup.cc (execute_cleanup_cfg_post_optimizing): Update
>> argument to make_forwarders_with_degenerate_phis.
> Not really working today, so not a review. Just a note that this fixes the
> SFB regressions on the RISC-V port as well.
IIRC we have similar code in path splitting. Can we try creating a helper that
works for both cases?
Richard
>
> jeff
